Abstract
In this study, response surface methodology was used for optimization of intermittent microwave–convective air drying (IMWC) parameters with employing desirability function. Optimization factors were air temperature (40–80°C), air velocity (1–2 m/sec), pulse ratio) PR ((2–6), and microwave power (200–600 W) while responses were rehydration ratio, bulk density, total phenol content (TPC), color change, and energy consumption. Minimum color change, bulk density, energy consumption, maximum rehydration ratio, and TPC were assumed as criteria for optimizing drying conditions of apple slices in IMWC. The optimum values of process variables were 1.78 m/sec air velocity, 40°C air temperature, PR 4.48, and 600 W microwave power that characterized by maximum desirability function (0.792) using Design expert 8.0. The air temperature and microwave power had significant effect on total responses, but the role of air velocity can be ignored. Generally, the results indicated that it was possible to obtain a higher desirability value if the microwave power and temperature, respectively, increase and decrease.
Highlights
Apple is the fourth major horticultural product of human nutrition in the world
Based on the results of (Soysal et al 2009b), the intermittent microwave–convective drying at 35°C with a pulse ratio of 3 at 597.20 W showed considerable savings in drying time and high-quality product with better physical and sensory attributes when compared to convective air drying
In terms of essential oil content and quality, the intermittent microwave– convective air drying (IMWC) at 25°C room temperature with the pulse ratio of 5 was provided as the most suitable drying method for oregano compared to CMWC drying, convective air dying, and shade drying (Soysal et al.2009a)
Summary
Apple is the fourth major horticultural product of human nutrition in the world. It is the pomaceous fruit of the apple tree, Malus domestica of the rose family of Rosaceae (Forsline et al 2003). Optimization IMWD with RSM to combine microwave drying with other drying methods including convective hot air, vacuum, and freeze drying to achieve more uniform, fast, and effective drying without valuable loss in quality (Wang et al 2004). Based on the results of (Soysal et al 2009b), the intermittent microwave–convective drying at 35°C with a pulse ratio of 3 at 597.20 W showed considerable savings in drying time and high-quality product with better physical (color and texture) and sensory attributes when compared to convective air drying. In terms of essential oil content and quality, the IMWC at 25°C room temperature with the pulse ratio of 5 was provided as the most suitable drying method for oregano compared to CMWC drying, convective air dying, and shade drying (Soysal et al.2009a). The overall objective of this study was to optimize the drying conditions of apple slices in IMCW drier and desirability function concept employed as the strategy for the optimization
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